| Main Ref. | Sabelli, B. and H.S. Feinberg (eds.), 1879 |
| Appearance refers to |
| specialized organs | |
| different appearance | |
| different colors | |
| remarks |
| Striking features | |
| Body shape lateral | |
| Cross section | |
| Dorsal head profile | |
| Type of eyes | |
| Type of mouth/snout | |
| Position of mouth | |
| Diagnosis | Shell: moderately swollen, thick and robust valves, almost circular, equivalved and inequilateral; has a thick dark brown to blackish periostracum; sculpture consists of thin concentric grooves; well-developed external ligament, reaching the end of the posterior margin of the valve, posterior to the umbones; hinge is heterodont, right and left valves each has three cardinal teeth, anterior and posterior lateral teeth; inside the valves are two slightly different muscle scars (dimyarian, anisomyarian), linked by a continuous pallial line (integropalliate), without a sinus; crossed-lamellae structure. Body: pair of gills each consists of two series of lamellae extensively linked by interlamellar junctions (eulamellibranch); foot is large and the two mantle lobes fuse to form two stout siphons. |
| Ease of Identification |
| Lateral Lines | Interrupted: No |
| Scales on lateral line | |
| Pored lateral line scales | |
| Scales in lateral series | |
| Scale rows above lateral line | |
| Scale rows below lateral line | |
| Scales around caudal peduncle | |
| Barbels | |
| Gill clefts (sharks/rays only) | |
| Gill rakers | |
| on lower limb | |
| on upper limb | |
| total | |
| Vertebrae | |
| preanal | |
| total |
| Attributes | |
| Fins number | |
| Finlets No. | Dorsal |
| Ventral | |
| Spines total | |
| Soft-rays total | |
| Adipose fin |
| Attributes |
| Fins number | |
| Spines total | |
| Soft-rays total |
| Pectoral | Attributes |
| spines | |
| soft-rays | |
| Pelvics | Attributes |
| Position | |
| spines | |
| soft-rays |